Extreme-pressure grease compositions



United Patent 3 370 007 EXTREME-PRESSURE cirnAsn coMrosmoNs Gerard P. Caruso, New Orleans, La., assignor to Shell Oil Company, New York, N.Y., a corporation of Delaware N0 Drawing. Filed Sept. 8, 1964, Ser. No. 395,024 14 Claims. (Cl. 25221) This invention relates to improved lubricating grease compositions. More particularly, the invention relates to greases gelled with water-proofed clays and containing extreme-pressure additives.

Plastic lubricating compositions suitable for general use throughout mechanical arts should possess good lubricating properties and, for heavy duty use, should also inherently possess extreme-pressure characteristics when operated in either a wet or dry environment. The former condition is particularly prevalent in such industrial uses as steel-rolling mill application and the like. However, some situations exist where only extreme-pressure action under dry conditions is required.

Certain greases gelled with clays contain small amounts of inorganic salts which are usually regarded as innocuous or undesirable contaminants. In the amounts in which they have been so found, their proportions have been too small to have any noticeable effect upon the extremepressure properties of clay greases.

It has been possible in the past to formulate clay grease compositions having good resistance to loss of physical characteristics by water as well as having desirable mechanical characteristics. The ability to operate under extreme loading, however, has not been satisfactorily obtained by the use of most well known extreme-pressure agents such as are employed in oil and soap thickened grease compositions.

Certain materials may be incorporated in the usual type of soap base greases for imparting extreme-pressure properties thereto, but when the same materials are incorporated in greases gelled with clays, it has been found that they cause undue softening and even liquefaction of the greases.

The incorporation of many materials of an entirely inorganic nature for the purpose of increasing load-bearing capacity is economically limited by the relatively high cost of such substances.

In applicants copending patent application Serial No. 383,503, now Patent No. 3,271,309, filed July 17, 1964, it is disclosed that greases gelled with oleophilic clay products may be improved with respect to their extremepressure properties by the presence of an efiective loadbearing proportion of a metal carbonate having a Moh hardness of 1-5 and a thermal decomposition above about 250 C. Another aspect of that invention comprises the finding that an unexpected improvement can be obtained by combining molybdenum disulfide, an amorphous antimony sulfide and/or a lead naphthenate therewith, thus enabling a drastic reduction in the carbonate requirement for a given Extreme-Pressure (EP) value.

Still another aspect of that invention lies in the discovery that greases gelled with oleophilic clay products can be improved with respect to their extreme-pressure properties under both wet and dry operating conditions by the combination therein of the above-mentioned metal carbonate and molybdenum disulfide, and/or an amorphous antimony sulfide, supplemented by a lead naphthenate. This aspect of the invention depends upon the finding that operation under wet conditions seriously degrades the effectiveness of the sulfide as an extreme-pressure agent (even though good dry operation is obtained), but that this can be corrected and even supplemented by the presence of a lead naphthenate. However, it has also been found that the proportion of naphthenate is restricted by Cal "ice

the deleterious effect of the naphthenate upon the consistency of the grease if it is present in more than strictly limited amounts as more fully described hereinafter. If greater than these limited amounts are employed, the grease structure may in fact even be destroyed.

Now, in accordance with the present invention, it has been found that certain saturated aliphatic carboxylic acid esters have the quite unexpected property of interaction with either or both the metal sulfide or the metal carbonate-EP additives in such a manner that the efficacy of the EP additives is improved stillfurther. This means, of course, that such esters may be used in either of two ways: (1) they can be added to raise the EP properties of clay-thickened greases containing either or both of the foregoing two EP additives, or (2) they can be added to such greases containing smaller amounts of the EP additives while maintaining the same level of EP effectiveness. Since the cost of the esters is considerably less than either the metal sulfide or the metal carbonates, considerable savings in cost can be obtained without any sacrifice in extreme-pressure properties of the grease in which they are used.

The esters which may be used in accordance with the invention are a quite narrow class of saturated aliphatic carboxylic acid esters corresponding to the formula 0 R g/0R1 wherein R is a normal alkyl radical having from 1 to 20 carbon atoms and R is likewise a normal alkyl radical but having only from 1 to 8 carbon atoms, the sum of R and R being at least 5. The esters are therefore neither substituted nor branched. It is preferred that R and R contain, respectively, from 16 to 18 and l to 6 carbon atoms. Butyl stearate is particularly preferred.

Broadly speaking, the metal carbonates which can be used herein are those having a hardness of 1-5 0n the Moh hardness scale and which do not decompose when heated in air up to at least 250 C. Metals having carbonates within this class comprise calcium, magnesium, manganese, iron, strontium, barium, lead, copper and zinc. Thus the metals are derived from groups IB, IIA, IVA, VIIB and VIII of the Periodic Table of the elements. Preferred metal carbonates are carbonates of the Group IIA alkaline earth metals and lead, of which calcium and lead carbonates are particularly preferred.

Either prepared or natural mineral carbonates may be used. In the latter case, the carbonate may be derived from more than one metal such as dolomite Other mineral carbonates having a Moh hardness of 1-5 which may therefore be employed include Ankerite [2CaCO MgCO FeCO Calcite and Aragonite (CaCO Cerussite (PbCO Azurite [2CuCO Cu(OH) Malachite Smithsonite (ZnCO Strontianite (SrCO Witherite (BaCO Zaratite [NiCO -2Ni(OH) -4H O], Magnesite (MgCO Rhodochrosite (MnCO and Siderite (FeCO Gay-Lussite (Na CO -CaCO 5 H O), Thenmonatrite (Na CO -H O), and sodium carbonate (Na CO Because severe EP conditions are usually accompanied by high temperatures, it is essential that the EP agents be chemically inert at high temperatures as to reaction with air. For this reason, metal carbonates decomposing on heating below about 250 C. are not satisfactory.

The alkaline earth metal carbonates which may be employed for use in the subject class of greases comprise particularly calcium, magnesium or barium carbonates and preferably are of a relatively cured nature, i.e., relatively free from abrasive impurities such as silica. Thus, precipitated chalk and the like are preferred. If the alkaline earth metal carbonate is the sole extreme-pressure agent present, it is preferred to employ amounts between about 3 and 7.5% based on the total grease compositions. These substantial proportions of the carbonate have been found to materially increase the load-bearing capacity of the grease although smaller amounts which may often have been present as impurities, have had no noticeable effect. For example, in the commercial preparation of clay for use as a grease gelling agent, it is often the practice to mechanically separate gangue from the crude clay. This often results in a small amount (in the order of 510% by weight of the dry clay) of calcite (calcium carbonate) remaining in the clay. This small amount is insufficient to cause any noticeable change in the extremepressure properties of greases eventually made from such clays. Other means for forming clay greases which involve more intricate manipulation completely eliminate the calcite impurities. Consequently, greases made from such clays contain no alkaline earth metal carbonates.

When utilized in conjunction with molybdenum sulfide, an amorphous antimony sulfide or a lead naphthenate, however, it has been found that the amount of metal carbonate may be drastically reduced, while at the same time retaining a substantial extreme-pressure property in the grease. Consequently, when either or both of these supplemental additives are present, the proportion of metal carbonate may be reduced to as little as about 0.05% and preferably is within the range of 0.3-1.5 based on the total grease composition.

The sulfides which may be used in conjunction with carbonate include molybdenum disulfide, an amorphous antimony sulfide and mixtures thereof. The amorphous antimony sulfide is specified as contrasted to the crystalline antimony sulfides. The latter, normally obtained by the mining of certain minerals such as stibnite, actually causes abrasion of metallic parts. This may be due either to the extreme hardness of crystals or may be due to natural-occurring impurities such as silicates or silica present in the mineral. The amorphous antimony sulfides (e.g., antimony trisulfide, antimony tetrasulfide, or antimony pentasulfide and mixtures thereof) vary in color from yellow to gray but usually are some variety of red, dependent upon the precise means of preparation and more particularly upon the particle size of the amorphous sulfide. They are preferably obtained by precipitation of the antimony sulfide from an aqueous solution of a watersoluble antimony salt, such as antimony chloride, by treatment with a sulfide such as sodium sulfide or hydrogen sulfide.

In order to effect satisfactory improvement in extremepressure properties of the subject class of greases, it is desirable to utilize 0.1-1.25% by weight of the sulfide. It is desirable to limit the proportion to this maximum figure due to the relatively high cost of the sulfide. It may be noted that, used in excessive amounts such as -25% by weight, sulfide may even perform a function of a grease gelling agent. However, the greases so produced are relatively unstable in structure and, of course, are excessively expensive due to the large amount of sulfide required for this purpose. In the proportion of 0.1-1.25% by weight, the sulfide does not perform any effective gelling or thickening of the clay grease, sufiicient oleophilic clay product always present to cause the formation of a grease structure of the compositions being considered.

As suggested above, the addition of molybdenum disulfide and/or amorphous antimony sulfide to clay grease containing metal carbonate promotes the extreme-pressure properties of the subject grease compositions and drastically reduces the carbonate requirement.- This is especially noteworthy when little or no water is present as an impurity or component of the greases. However, when the grease is contaminated with water, the effect of sulfide as an extreme-pressure additive is substantially degraded. Since wet operating conditions are often present where heavy loads are required, such as in steel mill operation, any satisfactory grease composition must be capable of providing extreme-pressure lubrication even when water is present.

Consequently, lead naphthenate is used to supplement the carbonate (with or without sulfide) and performs the function of maintaining the extreme-pressure properties of the grease experienced under dry conditions and, with antimony sulfide, even unexpectedly promotes still higher extreme-pressure properties under wet conditions. It is noted hereinabove that it is necessary to restrict the proportion of lead naphthenate, said proportion to be between about 0.1 and about 0.75% lead naphthenate based on the weight of the total grease composition.

Lead naphthenates are materials which are well known and may be prepared by reaction of lead compounds with naphthenic acids such as those obtained from certain American crudes, especially those obtained from California crudes. The naphthenic acids are obtained as mixtures and have average molecular weights of about 250 or higher, generally 250-1000. In producing lead naphthenate, the requisite amount of a lead oxide, such as litharge, is added to the acids and the temperature is raised sufficiently to eifect reaction. The proportion of lead in the finished product is in the order of 25-35% by weight. It is preferred to make the lead naphthenate from the oxide instead of utilizing other lead salts, although salts such as lead carbonate may be employed if desired.

The clays which are useful for the preparation of the subject oleophilic clay products are those exhibiting a substantial base exchange capacity. The clays particularly contemplated herein include especially the montmorillonites, such as sodium, potassium, lithium, and the other bentonites, particularly of the Wyoming bentonite type. Still more preferred are the magnesium bentonites, sometimes referred to as hectorites. These clays are characterized by unbalanced crystal structure and are believed to have negative charges which are normally neutralized by inorganic cations.

The term oleophilic clay product is meant to include such clays when they have absorbed thereon or reacted therewith sufiicient organic ammonia base to form an oleophilic product. The so-called onium-clays comprise reaction products of oleophilic ammonium bases (or their salts) and clay.

The clays are more preferably modified by absorption of one or more oleophilic cationic surface-active agents such as those described in US. Patents 2,831,809, and 2,875,152. The clays are preferably present in an amount sufficient to cause grease formation of the lubricating oil to occur. This will usually occur in the range of 25-10% by weight of the high base exchange clay (based on the inorganic clay portion of the oleophilic clay product) dependent somewhat upon the precise clay employed, the chemical constitution of the major lubricating oil components and the proportions of other components present in the grease formulation.

Particularly preferred organic ammonia bases are selected from the group consisting of imidazolines, amino amides formed between certain fatty acids and a mixture of polyethylene polyamines, and mixtures of such imidazolines and aminoamides.

The imidazolines which constitute one of the two preferred classes of clay waterproofants are those substituted with an organic radical of such dimensions as to provide the imidazoline with oleophilic properties. The substituent group or groups may be hydrocarbyl, alkyl, allyl or amino groups of which the following are exemplary:

IMIDAZOLINES H ydrocarbyl-substitmed 2-heptadecenyl imidazoline Z-undecyl imidazoline 2-octadecyl imidazoline 2-dodecyl imidazoline 2-tetradecyl-4,5-dimethyl imidazoline 4-heptadeceny1 imidazoline 4-octadecyl imidazoline 4-hexadecyl-2-butyl imidazoline A lkylol-substituted:

148-hydroxyethyl-2-heptadecenyl imidazoline Z-B-hydroxyethyl-4-undecyl imidazoline 4-,B-hydroxyethyl-l-heptadecyl imidazoline 1-fi-hydroxybutyl-2-heptadecyl imidazoline 2-a-hydroxyhexyl-4-dodecenyl imidazoline l-B-hydroxyethyl-2-undecyl imidazoline l-fi-hydroxyethyl-2-mixed 'heptadecenyl and heptadecadienyl imidazoline Amino-substituted:

1-/3-aminoethyl-2-heptadecenyl imidazoline 2-B-aminoethyl-4-octadecyl imidazoline l-triethylene triamino-Z-heptadecyl imidazoline 1-diethylenediamino-2-hexadecyl imidazoline 1-imidazolino-2-heptadecyl imidazoline It is preferred that the hydrocarbyl substituted imidazolines are those in which the oleophilic radical is one having from 10 to 20 carbon atoms. The imidazolines may be substituted in other positions by other groups which do not directly influence the oleophilic character of the imidazoline to a major extent. The preferred class of hydrocarbyl substituted imidazolines are those in which the long chain hydrocarbyl substituent is located at the two position, that is, the carbon atom which separates the two nitrogen ring atoms of the imidazoline nucleus.

The alkylol-substituted imidazolines are those in which the alkylol group is one having from about 1 to 20 carbon atoms bearing at least one hydroxyl radical. The preferred class of such materials are those in which the alkylol radical has from 2 to 6 carbon atoms and 1 hydroxyl radical, the oleophilic character of the imidazoline being supplemented by a long-chain hydrocarbyl substituent on another ring carbon atom, preferably in the 2-position. Still more preferred is 4-12% by weight of phosphoric acid (roughly equivalent to the base exchange capacity of the clay). modifying the mixture with the oleophilic nitrogen compound and drying the mixture so obtained at temperatures between 300 and 1400 F. so as to obtain a product having fine division (must pass 250 mesh) and containing 0.1-5.0% by weight water. The striking feature of the products and particularly of products so produced comprises their ability to be dispersed in their oleophilic end use medium, such as lubricating oil, by the use of homogenization at ambient temperatures, usually l5-20 C.

The amino amides which constitute the other of the two preferred classes of hydrophobing agents are formed between fatty acids having -20 carbon atoms per molecule and a mixture of polyethylene polyamines, 20-80% by weight of the mixture comprising 20-80% (but preferably less than 50%) of diethylene triamine, the remaining fraction being polyethylene polyamines having an average molecular weight within the range 220-450, the amino amides having been formed by reaction of 30-75% by weight polyamines and 70-25% by weight of fatty acids at 200-225 C. for a reaction period of 1 to 4 hours.

Both saturated and unsaturated fatty acids :and mixtures thereof may be used in the amino amide. However, a different range of molecular weights for the fatty .acids are preferred, depending on whether they are predominantly saturated or unsaturated.

When at least 50% by weight of the fatty acids contain at least 1 double bond per molecule, it is preferred to use C1640 fatty acids. On the other hand, when predominately saturated fatty acids are used, i.e., those acids having an iodine value of 60 or below, it is preferred to use C1048 fatty acids. 1

Though essentially completely saturated or unsaturated acids can be used within the foregoing carbon number limitations, it will normally be preferred to use mixtures of fatty acids both as to unsaturation and carbon number since they are considerably less expensive and no less effective.

The cationic hydrophobic surface active agent (or hydrophobing amino radicals) is to be utilized in an amount between about 2.5 and about 5% by weight based on the total grease composition, the amount being suflicient to provide the clay with substantial hydrophobic properties. By the later is meant the stability of the clay to maintain its grease structure even when the later is contaminated with water.

The major component of the grease compositions is of course the lubricating oil. The oil component in the greases may be any of the oils of lubricating grades normally utilized in compounding grease compositions. They may be refined, unrefined or semi-refined, paraflinic, naphthenic or asphaltic base mineral oil having viscosities of 50-4000 S.S.U. at F. Synthetic lubricants may be used in place of or in addition to mineral oils. Various classes of synthetic lubricants are known in the art and include particularly aliphatic dicarboxyli-c esters such as bis(2-ethyl hexyl) sebacate, aliphatic silicates, fluorates and phosphates.

Optional ingredients which may be included in the grease compositions are those employed for promoting oxidation stability and corrosion protection. Aromatic amines are known for their oxidation stabilizing properties and include especially the phenyl and naphthyl amines, including diphenyl amine, phenyl alpha-naphthylamine, phenyl beta-naphthylamine as well as their analogs and homologs. Suitable corrosion inhibitors include particularly the alkali metal nitrites such as sodium and potassium nitrite and the reaction products of terpenes with a phosphorous halide such as phosphorous chlorides. It is preferred that a supplementary additive as described above be present in an amount between 0.1 and 1.0% by weight based on the total grease composition.

The greases may be prepared by any suitable means known to the art but the most efiicient preparation is one which utilizes the so-called direct transfer process. The steps involved in this process may be described briefly as follows: Clay is dispersed in water to form a 1-4% aqueous dispersion from which the gangue may be separated by sedimentation or centrifuging to obtain a purified dispersion of the clay containing about 10% by weight of calcite. The aqueous clay dispersion is then combined with the hydrophobic surfactant and at least part of the mineral oil component, together with sufficient agitation to cause intimate surface contact of the ingredients for the purpose of enabling adsorption of the surfactant upon the surfaces of the clay. The oleophilic clay product associates with the oil and separates from a major proportion of the water. The remaining oil and oleophilic clay product, which is still wet, is heated to a point sufficient to cause substantially all of the water to evaporate. The components are subjected to a high rate of shear, either during water evaporation or subsequent thereto, during which time any remaining desired lubricating oil may be added.

The extreme-pressure agents, namely, the metal carbonate, sulfide, ester and lead naphthenate, may be added at any suitable stage in the process, but it is preferred that they be incorporated subsequent to water removal. The

calcium carbonate remaining after gangue removal may constitute all or part of the carbonate required. The agents may be added as dry materials, either separately or together, but more preferably they are added as an oil slurry or concentrate to the otherwise finished grease composition. While it is possible to obtain satisfactory results by mere incorporation and homogenizing, it is preferred that the grease composition so modified be subjected to a high rate of shear since it has been found that this increases the effectiveness of the extreme-pressure agents,

the weight of the clay, of an amino amide formed between tall oil fatty acids and the mixture of polyethylene polyamines described hereinbefore as the bottoms product obtained in the preparation of ethylene diamine.

In each of the grease blends shown in the following table, the carboxylic acid ester was butyl stearate.

TABLE I Metal Carbonate Dry Timken Wet Timken Test 1 Test 1 1 Timken Extreme Pressure Test, AS'IM Bulletin 228, February 1958, pages 28-31.

probably due to the more thorough dispersion thereof throughout the grease composition.

The compositions of the invention therefore consist essentially of a major proportion of lubricating oil gelled to grease consistency by means of an oleophilic clay product, which has been rendered oleophilic by treatment of a clay having a base exchange capacity with an organic ammonia base, and, based on the total weight of the grease composition, (a) 0.25-5.0% of a carboxylic acid ester cor-responding to the formula wherein R is a n-alkyl radical having from 2 to carbon atoms and R is a n-alkyl radical having from 1 to 8 carbon atoms, and (b) at least 0.25% each of at least one primary extreme-pressure additive selected from the group consisting of metal carbonate having a Moh hardness of at least 3 and a thermal decomposition temperature of no less than 250 C. amorphous antimony sulfide and molybdenum di-sulfide.

The greatest degree of EP effectiveness per unit of ester used is from about 0.5 to about 3.0% by weight of the grease composition. Within this narrow concentration range, the amount of ester will be governed by the EP level sought and the relative EP activity of the primary EP additive components, i.e., the metal carbonates or sulfides.

While it is necessary to use at least 0.25 of each of the primary EP additives, whether they are used singly or as mixtures, it is preferred to use at least about 0.5-3.0% for greater EP eifectiveness. It is, however, still further preferred to use no more than about 1.25% each of the metal sulfides and, especially in the case of the amorphous antimony sulfide, no more than about 0.85% is sufiicient and, therefore, prefrred. For economic reasons, it is, of course, preferred to minimize the amounts of the primary EP additives. The lead naphthenate need not be used in the composition of the invention in all cases, but when it is, it is preferred to be used in concentrations of (Ll-0.75% and more preferably 0.35-0.60%.

The following examples illustrate the unique interaction of the above-described carboxylic acid esters in claythickened greases containing metal carbonate and sulfide primary EP additives.

EXAMPLE I For the purpose of comparison, mineral oils were utilized throughout the following examples, all of the grease contained hectorite clay waterproofed with 60%, based on The above data show that the ester, by itself, has no EP activity in clay-thickened grease. In fact, it appears by comparison of the base grease with grease B that the ester is at least slightly detrimental to EP properties. On the other hand, by comparison of grease A with the base grease, it is shown that the lead carbonate increased the EP properties of the base grease. However, by using the ester in conjunction with the carbonate primary EP additive, the EP properties of the base grease were more than doubled. In fact, by using slightly higher amounts of the ester, even the EP properties of the grease containing the carbonate EP agent was more than doubled. It is important, too, to note that grease F containing the ester as well as the carbonate had quite excellent wet EP properties.

The efiect was also observed to practically the same magnitude when the primary EP additive was changed to calcium or sodium carbonate.

EXAMPLE II Samples of the basic grease of Example I were prepared, modified as indicated in the table below and tested for their EP properties.

TABLE II Ester, Metal Carbonate Dry Timken Grease percent Test Composition Percent wt. Pass Fail None 20 25 None 20 EXAMPLE III The same procedures of the previous examples were employed except amorphous antimony sulfide was used as the primary EP agent in place of the metal carbonates. The results of the EP tests were as follows:

TABLE III Ester, Metal Sulfide Dry Timken Wet Timken Grease percent Test Test Composition Percent wt. Pass Fail Pass Fail None None 20 25 None SbzS; 0. 75 50 55 0. 75 None 20 25 2. None 0.75 SbzSa 0.75 50 55 0. 75 SbzSs 0. 75 60 The above data are most interesting in that a somewhat different interaction seems to occur between the metal sulfide and the ester. Whereas, the ester has little if any elfect on the dry EP properties of the metal sulfide-containing grease (compare I with M and N), it nevertheless incurs truly phenomenal increases in the Wet EP properties of the grease.

It is also interesting to note from the above data that the amount of ester above about 0.75% had no eflfect on the grease containing no primary EP agents. Thereapplications of the greases, it is further preferred that they contain at least six total carbon atoms. Thus the sum of R and R should be at least 5.

EXAMPLE V Examples of other grease compositions exhibiting excellent EP properties as a result of this unique interaction of carboxylic acid esters with metal carbonate and sulfide primary EP agents are the basic greases of Example I containing the following additives:

TABLE V Primary EP Additive Ester Lead Naph- Composition thenate,

Percent wt. Composition Percent wt. Percent wt.

n-Propyl stearate n-O ctyl stearate n-Hexyl palmita n-Pentyl myristate n-Butyl stearate n-Pentyl palmitate n-Butyl eicosano ate n-Butyl heptadecanoate. n-Butyl palrnitate n-Bntyl pentadecanoate. Ethyl palmitate n-Hexyl valerate n-Bntyl deeano ate n NiCO3-2Ni(OH)2-4H2O 2CuCOa-C8.(OH)7 SbzSa fore, further confirmation is given that the carboxylic acid esters of the invention are essentially ineffective to benefit the EP properties of a grease in the absence of a metal carbonate or metal sulfide primary EP agent.

EXAMPLE IV Again using amorphous antimony sulfide as the primary EP agent in the base grease of Example I, a number of different esters were each added to separate samples of the antimony-sulfide-containing grease to determine their effectiveness to augment the EP eifect of the metal sulfide. The results were as follows: with the lubricated metal surfaces to produce a coating TABLE IV Ester Dry 'Iimken Wet Timken Grease SbzS per- Test Test cent wt. Composition Percent wt. Pass Fail Base-.- None 0. 75 50 Q Methyl stearate 0.6 0.6 R .do 0.75 0.6 60+ S Butyl stearate 0.75 0.75 60+ Hexyl stearate. 0.5 0.5 60+ Butyl acetate 0.75 0.75 60+ Butyl oleate 0.5 0. 5 40 45 Dioetyl sebacate 0.75 0. 20 Didecyl phtha1ate.. O. 5 0. 5 35 40 These data indicate that a wide range of saturated fatty acid esters are effective to augment the EP activity of metal sulfides, but that unsaturated or dicarboxylic acid esters do not possess this property to any discernible degree. Thus, saturated aliphatic monocarboxylic acid esters may be used having the formula II moon,

in which R is a C normal alkyl radical and R is a C normal alkyl radical. In order that the esters not be volatilized during grease processing or high-temperature which will either bear the load or at least prevent Welding of the lubricated surfaces. Thus, the mechanism by which the unsubstituted carboxylic acid esters of this invention make the metal carbonate and sulfide EP additives more effective is not understood.

I claim as my invention:

1. A grease composition consisting essentially of a major proportion of lubricating oil gelled to grease consistency by means of an oleophilic clay product which has been rendered oleophilic by treatment of a montmorillonite clay with an organic ammonia base, and, based on l 1 the total weight of the grease composition, (a) 0.255.0% of a carboxylic acid ester corresponding to the formula II IMG 0132 wherein R is a n-alkyl radical having from 16 to 18 carbon atoms and R is a n-alkyl radical having from 1 to 6 carbon atoms, and (b) at least 0.25% each of at least one primary extreme-pressure additive selected from the group consisting of metal carbonates having a Mob hardness of 1-5 and a thermal decomposition tempera ture of no less than 250 C., amorphous antimony sulfide and molybdenum disulfide.

2. The composition of claim 1 in which the carboxylic acid ester is butyl stearate.

3. The composition of claim 1 in which the extremepressure additive is 0.257.5% of a metal carbonate.

4. The composition of claim 1 in which the extremepressure additive is amorphous antimony sulfide.

5. The composition of claim 1 in which the extremepressure additive is molybdenum disulfide.

6. The composition of claim 1 in which the extreme pressure additive is lead carbonate.

7. The composition of claim 1 in which the extremepressure additive is calcium carbonate.

8. The composition of claim 1 in which the extremepressure additive is sodium carbonate.

9. The composition of claim 1 which contains, in addition, 0.1-0.75 of a lead naphthenate.

10. The composition of claim 9 in which the lead naphthenate is lead petroleum naphthenate.

11. A grease composition consisting essentially of a major proportion of lubricating oil gelled to grease consistency by means of an oleophilic clay product Which has been rendered oleophilic by treatment of a montmorillonite with an organic ammonia base, and, based on the total weight of the grease composition, (a) 0*.5-3.0%

12 of n-butyl stearate and (b) 0.5-0.85% of amorphous antimony sulfide.

12. A grease composition consisting essentially of a major proportion of lubricating oil gelled to grease consistency by means of an oleophilic clay product which has been rendered oleophilic by treatment of montmorillonite clay with an organic ammonia base, and, based on the total weight of the grease composition, (a) 0.5- 3.0% of n-butyl stearate and (b) 0.53.0% of lead carbonate.

13. A grease composition consisting essentially of a major proportion of lubricating oil gelled to grease consistency by means of an oleophilic clay product which has been rendered oleophilic by treatment of a montmorillonite clay with an organic ammonia base, and, based on the total weight of the grease composition, (a) 0.5- 30% of n-butyl stearate and (b) 05-30% each of lead carbonate and amorphous antimony sulfide.

14. The composition of claim 12 which contains 0.1- 0.75% of lead petroleum naphthenate.

References Cited UNITED STATES PATENTS 3,015,623 1/1962 Loring et al 252--18 3,095,376 6/1963 Hook et al. 25237.7 2,113,752 4/1938 Wiezevich 252-56 2,186,646 1/1940 Lincoln et al. 25256 2,210,140 8/1940 Colbeth 25256 2,370,299 2/ 1945 Farrington 252-56 OTHER REFERENCES Gear and Transmission Lubricants by Boner, Reinhold Pub. Corp., New York, 1964, p. 89.

DANIEL E. WYMAN, Primary Examiner.

I. VAUGHN, Assistant Examiner. 

1. A GREASE COMPOSITION CONSISTING ESSENTIALLY OF A MAJOR PROPORTION OF LUBRICATING OIL GELLED TO GREASE CONSISTENCY BY MEANS OF AN OLEOPHILIC CLAY PRODUCT WHICH HAS BEEN RENDERED OLEOPHILIC BY TREATMENT OF A MONTMORILLONITE CLAY WITH AN ORGANIC AMMONIA BASE, AND BASED ON THE TOTAL WEIGHT OF THE GREASE COMPOSITION, (A) 0.25-5.0% OF A CARBOXYLIC ACID ESTER CORRESPONDING TO THE FORMUAL
 9. THE COMPOSITION OF CLAIM 1 WHICH CONTAINS, IN ADDITION, 0.1-0.75% OF A LEAD NAPHTHENATE. 